In the past week, world leaders have started using a mathematical term when they talk about the Ebola epidemic in West Africa.It's spreading and growing exponentially, President Obama said Tuesday.This is a disease outbreak that is advancing in an exponential fashion, said Dr. David Nabarro, who is heading the U.N.'s effort against Ebola.So what does this mean?If nothing changes in the next few weeks, we could see at least 60,000 cases by the end of 2014.Here's why.Right now we've had more than 5,000 cases of Ebola, and at least 2,600 people have died.Some scientists, like Alessandro Vespignani at Northeastern University in Boston, are taking numbers like thatand putting them into computer models to see where this epidemic is going.For instance, in our modeling, by mid-October, we're already between 10,000 to 25,000 cases, he says.Five thousand cases of Ebola is bad; 10,000 to 25,000 is unbelievable.And that's where the exponential curve comes into play.Well, an exponential curve is a curve that doubles every certain amount of time, Vespignani says.And with this outbreak, cases are doubling every three to four weeks.So if help doesn't arrive in time ― and the growth rate stays the same ―then 15,000 Ebola cases in mid-October could turn into 30,000 cases by mid-November, and 60,000 cases by mid-December.And you see that right away you get very scary numbers, Vespignani says.So every day or week that goes by, the epidemic gets harder and harder to control.
上周，世界领导人在谈论西非国家的埃博拉疫情时开始使用数学用语。它正在成倍地传播和增长，奥巴马总统周二表示。联合国对抗埃博拉的负责人大卫・纳瓦尔表示，这个疾病目前正在呈指数增长。这是什么意思？如果未来几周没有发生变化，那截至2014年底，我们会看到至少6万例埃博拉病例。下面解释原因。目前感染埃博拉病毒的病例超过5000例，其中至少有2600人死亡。一些科学家，比如美国波士顿东北大学的亚历山德罗・维斯皮纳尼正在处理这些数据，他们将数据带进计算机模型，以观察这一疫情的发展轨道。举例来说，在我们的模型中，到10月中旬我们将有1万至2.5万起病例。5000例埃博拉病例已经很可怕了；1万至2.5万起病例简直难以置信。这就是指数曲线在发挥作用。维斯皮纳尼表示，指数曲线是在特定时间增倍的曲线图。就这个病毒来说，病例会在每三到四周的时间加倍。所以，如果救助不及时抵达，那增长率就会继续保持，而到十月中旬就会有1.5万例埃博拉病毒，11月中旬这个数字会达到3万例，十二月中旬会有6万例。维斯皮纳尼表示，你马上就会看到这个可怕的数字。随着时间的推移，疫情变得越来越难以控制。
暂无注释
